Effect Of Energy Dissipation Research Articles

Hot Plastic Deformation of Titanium Alloys Reflected on Process Maps

Maps are plotted for the hot plastic deformation of titanium-based alloys with a high-temperature polymorphic transformation, namely, martensitic 23A, 5VA and PT3V alloys. Hot plastic compression is modeled using a DIL 805 A/D dilatometer. Samples in the form of ∅5 × 10 mm cylinders are compressed to a strain of 0.3 in the temperature range 600–1100°C at a strain rate from 10–3 to 10 s–1. The α ↔ β transformation temperatures are 800–900°C in alloy 23A, 880–900°C in 5VA, and 900–920°C in PT3V, and they fall into the temperature range of hot compression. The process maps show the effect of mechanical energy dissipation in changing the shape and structure of the samples. The dissipation of introduced mechanical energy is found to be due to the operation of the following two structural mechanisms: accommodative elastoplastic relaxation in ensembles of lattice defects with η ≈ 25% and the hcp ↔ bcc crystallographic transformation with an efficiency η ≈ 15%.

Seismic performance improvement of ±800 kV UHV DC wall busing using friction ring spring dampers

Wall bushings that connect converter valves within hall buildings and other electric facilities in a direct current (DC) field are indispensable in substations but vulnerable to earthquakes. A finite element model was developed to evaluate the seismic performance of a real ultra-high-voltage (UHV) DC wall bushing. The numerical results show that the maximum stress of the wall bushing during seismic activity does not satisfy the strength safety factor provisions within Chinese regulations. To improve the seismic performance of the wall bushing, an energy dissipation device composed of eight friction ring spring dampers (FRSDs) was proposed to be installed between the connection plate on which the bushing is mounted and a steel wall frame. In addition, optimum parameters of the FRSDs were researched and determined, then the seismic responses of the wall bushing with and without the FRSDs were compared to evaluate the energy dissipation effects. Full-scale shaking table tests were conducted on a wall bushing with the designed energy dissipation device. The validity of the numerical simulations and effectiveness of the proposed energy dissipation device of the wall bushing were verified by the experimental results in terms of seismic response mitigation.

The effect of energy dissipation on the dynamic response of reinforced concrete structure

Solving problems associated with protecting buildings from progressive collapse and minimizing resources is becoming increasingly important. In many countries, ensuring such protection is set in accordance with the requirements of national regulatory documents and, therefore, researches aimed at developing effective ways to protect constructive systems from progressive collapse under special actions are relevant. In this regard, the present work presents studies of the influence of energy dissipation in constructive reinforced concrete elements during their sudden structural rearrangement caused by the removal of one of the supporting elements. The hysteretic dispersion accompanying the nonlinear load-unload cycle of the cross-section during crack formation is taken into account. The damping mechanism of reinforced concrete elements of the constructive system is described by the equivalent viscous damping model, based on the hypothesis of proportionality of the damping force and the oscillation velocity. Approbation of the calculated model is carried out in relation to the reinforced concrete frame structures, the physical models of which were tested under the considered loading regime. A comparison of the experimental and calculated parameters shows the effectiveness of the proposed model for assessing the dynamic response of reinforced concrete structures with cracks under the static-dynamic loading regime.

On the possible of the abnormally high damping effective properties of dispersion-reinforced composites and fibrous composites

We study the effective energy dissipation properties of solid polymer matrixes filled with coated spherical and fibrous inclusions coated with a layer of lossy viscoelastic material. The matrix and the inclusions are assumed to be separated by equal-thickness interfacial layers of a lossy viscoelastic material. We show that the remarkable loss amplification mechanism is operative in such particulate-morphology materials when the effective loss properties of composite can exceed the loss properties of the pure matrix by more than 20 times.

A highly elastic and sensitive sensor based on GSP/HPAM composited hydrogel

AbstractDevelopment of conductive hydrogels to mimic the structures and properties of human skin has attracted enormous scientific interests. However, applications of such materials are often restricted by their poor mechanics and moderate sensitivities. Herein, a highly‐stretchable, self‐healing, and conductive hydrogel, comprised of grape seed extracted polymer and hydrophobically associated polyacrylamide (GSP‐HPAM), was fabricated by simple mixing and in‐situ polymerization. Compared with the single HPAM gels, the rigid GSP polymer could form sufficient hydrogen bonds and ionic interactions, which endowed the gel with effective energy dissipation mechanism and greatly improved the uniformity of network. As a result, the GSP‐HPAM gel exhibited enhanced mechanics, that is, the tensile strength, strain, and compression stress of GSP‐HPAM hydrogel were 0.7 MPa, 3000% and 28.3 MPa, respectively. Furthermore, the gel demonstrated linear strain‐dependant conductivity between 0% and 1000% with gauge factor around 3.43, superior to most hydrogel‐based strain sensors. In addition, the gel was able to monitor human body motion, such as, finger bending and pulse rate. This multiple functional gel might find potential applications in artificial skin, soft robotics, and wearable devices.

Dynamics of a regularized and bistable Ericksen bar using an extended Lagrangian approach

The motivation of this work is to better understand the dynamic behaviour of bistable structures presenting an analogy with regularized Ericksen bars. The archetype of such structures is the bistable tape spring, which exhibits a particular scenario of deployment, from the stable coiled configuration to the straight stable configuration: at each time of the deployment, the geometry of the tape is similar to a two-phase bar with a coiled part and a straight part separated by a transition zone that moves along the tape. One goal of this work is to show that a regularized and bistable Ericksen bar model contains all the properties to reproduce such a dynamic behaviour. The mathematical structure of this model presents a locally non-convex potential with two minima and a dependence of higher order terms. Some similarities exist between this model and the Euler-Korteweg system with a Van der Waals equation. To study numerically the dynamic behaviour of such models, it is necessary to solve a dispersive and conditionally hyperbolic system. For this purpose, the Lagrangian of the regularized bistable Ericksen model is extended and penalized. Variable boundary conditions are deduced from Hamilton’s principle and are used to control the evolution of the system. Dispersion analysis allows to determine the numerical parameters of the model. The obtained non–homogeneous hyperbolic system can be solved by standard splitting strategy and finite-volume methods. Numerical simulations illustrate how the parameters of the model influence the width and the propagation speed of the transition zone. The effect of energy dissipation is also examined. Finally, comparisons with an exact kink wave solution indicate that the extended Lagrangian solution reproduces well the dynamics of the original Lagrangian.

The Effects of Energy Dissipation of the Closure Bolted Joints Under Vibration Behavior

Abstract Bolted joints are widely used in mechanical construction due to their ease of disassembly. When the bolting member is subjected to the alternating load, the pretightening force is gradually reduced, which may cause the interface contact performance to decrease, and the surface may be microslipped. Preload relaxation of threaded fasteners is the main factor that influences the joint failure under normal cyclic loading, but it is difficult to monitor the energy dissipation between the interface of the bolted joint. This paper presents an energy dissipation model for the bolted joint based on two-degree-of-freedom vibration differential mathematical model. The parameters of the model is calculated by using the fractal theory and differential operator method. The efficiency of the proposed model is verified by experiments. The results show that the experimental modal shape agrees well with the theoretical modal shape. According to the change of cyclic load and vibration frequency, the vibration response and the law of energy dissipation under different factors can be obtained. The results show that the vibration frequency and cyclic load are the main factors affecting the energy dissipation between interfaces. The energy dissipation of the contact surface of the bolted joints account for the main part of the energy dissipation of the bolted structure. The results provide a theoretical basis for reducing the looseness of the bolt connection and ensuring the reliability of the equipment.

Highly sensitive, stretchable and durable strain sensors based on conductive double‐network polymer hydrogels

AbstractHydrogel‐based strain sensors have been attracting immense attention for wearable electronic devices owing to their intrinsic soft characteristics and flexibility. However, developing hydrogel sensors with hightensile strength, stretchability, and strain sensitivity remains a great challenge. Herein, we report a technique to synthesize highly sensitive hydrogel‐based strain sensors by integrating carbon nanofibers (CNFs) with a double‐network (DN) polymer hydrogel matrix comprising of a physically cross‐linked agar network and a covalently cross‐linked polyacrylamide (PAAm) network. The resultant nanocomposite sensors display superior piezoresistive sensitivity with a hightrue gauge factor (GFT = 1.78) at an ultrahigh strain of 1,000%, a fast response time and linear correlation of ln(R/R0) and ln(L/L0) up to 1,000% strain. Most significantly, these sensors possess highmechanical strength (~0.6 MPa) and superb durability (>1,000 cycles at strain of 100%), stemming from the effective energy dissipation mechanism of the first agar network acting as sacrificial bonds and the CNFs serving as dynamic nanofillers. The combination of highstrain sensitivity and ultrahigh stretchability of hydrogel sensors makes it possible to sense both small mechanical deformations induced by human motions and large strain up to 1,000%.

Experimental evaluation of the shore protection potential of the novel REEFS wave energy converter

REEFS is a novel multipurpose patented wave energy converter (WEC) that combines electric energy production with shore protection. The device shows some similarities with natural reefs and detached submerged breakwaters. However, unlike previous ones it is installed with an orthogonal alignment relative to coast line and with a greater freeboard. Exterior stay vanes, are another distinct characteristic of the device. Therefore, the REEFS differentiating functionality of shore protection cannot be directly extrapolated from detached submerged breakwater studies and the effective energy dissipation capacity of this new WEC taking into account its specific characteristics should be investigated. In this article an experimental investigation of the energy dissipation potential of REEFS WEC was implemented. A small scale physical model (1.5:100) was installed in a piston wavemaker flume and tested under regular wave conditions established by applying Froude similarity to typical West Portuguese sea state conditions. Resistive wave gauges were installed upstream and downstream the device, in order to record water level time series. Discrete Fourier transform technique was used to compute the wave energy spectra (WES). Energy dissipation was evaluated by comparing upstream and downstream WES. Two versions of the device were tested: i) without exterior stay vanes; ii) with exterior stay vanes. Regardless of the version, the REEFS model proved to be able to dissipate part of the incident wave energy. This capacity exhibited a dependence on the wave period, globally decreasing as the wave period increased. The version equipped with stay vanes always exhibited a substantially higher energy dissipation. From a relative point of view, stay vanes showed to be more important for long waves. REEFS energy dissipation was not far from the inferior values reported in literature review for submerged breakwaters of comparable dimensions, confirming the expectations about its shore protection functionality.

From deformation localization to melting and chemical segregation in metallic glass nanoparticles under high strain rate

Nanoparticles possess many distinguished properties due to their small size and unique internal and surface structures. For metallic glass nanoparticles, the small size combined with disordered atomic structure results in many unexpected results, some of which are superior to crystalline particles. This field, however, remains largely unexplored. Here, we report the mechanical and thermomechanical responses caused by the increasing strain rate in metallic glass nanoparticles under compression. The mechanical properties of nanoparticles resemble those of the bulk when the strain rate is below 1010 s−1; above this threshold, the nanoparticle exhibits localized deformation and then melting and even chemical segregation at the contact surface area. We reveal that these unique behaviors are the direct results of the lack of effective energy dissipation mechanisms in the disordered materials that are different from crystalline nanoparticles.

Steel A-braced frame upgrade performance under various load characteristics

This study evaluated innovated A-braced frame design performance under cyclic load and twelve far-field and near-field earthquake ground motions. The proposed A-brace design combined pre-deformed brace segments, steel curved damper and lever mechanism to amplify steel curved damper deformation for effective energy dissipation. A series of cyclic loading tests on steel moment resisting frames with the proposed A-braces were conducted first. The cyclic load test results showed that A-braced frames exhibited higher stiffness than the moment resisting frame in both elastic and inelastic stages to effectively reduce the structural deformation. Significant strength and energy dissipation enhancements were achieved in A-braced frames, with maximum gains reaching 2.31 and 1.94 times, respectively, above those of the moment resisting frame. Seismic performance evaluation on multi-story framed structures revealed that lower structural base shear, reduction in story drift, approximately 30.86%, 27.61% and 27.51% for the 10, 6 and 3-story frames, respectively, and plastic hinge development elimination to prevent structural failure were achieved simultaneously when the A-brace was adopted. The A-braced frame performance enhancements under cyclic load and various earthquake ground motions effectively justified proposed method applicability to seismic structural design.

High-Strength and High-Toughness Silk Fibroin Hydrogels: A Strategy Using Dynamic Host-Guest Interactions.

Natural polymer-based hydrogels attract great attention because of their inherent biocompatibility and controllable biodegradability. However, the broad applications of these hydrogels require a combination of high mechanical strength, high toughness, fatigue resistance, as well as self-healing. The integration of this combination into one natural polymer-based hydrogel remains challenging. Here, a molecular design strategy was proposed to fabricate mechanically robust silk fibroin-based hydrogels using host-guest interactions. Silk fibroin molecules was chemically modified with cholesterol (Chol, guest) or β-cyclodextrin (β-CD, host), and host-guest interaction between Chol and β-CD moieties drove the supramolecular assemblies of hydrogels. The dissociation/reassociation behavior of host-guest complexation, serving as sacrificial bonds, endowed hydrogels with effective energy dissipation and rapid self-healing ability. The prepared silk fibroin-based hydrogels exhibited high mechanical strength, high toughness, and remarkable fatigue resistance, superior to conventional silk fibroin hydrogels. Moreover, due to reversible host-guest interactions, hydrogels achieved facile functional recovery after damage without any external stimuli. This design strategy provides an avenue to develop natural polymer-based materials with robust mechanical properties, thus broadening current hydrogel applications.

Engineering entanglement, geometric phase, and quantum Fisher information of a three‐level system with energy dissipation

Quantum Fisher information (QFI) and geometric phase have recently performed different tasks in quantum information technology. We investigate the statistical quantities as the QFI and entanglement of a three‐level atom in Λ configuration interacting with a quantized field mode by using linear entropy. We study the dynamical behavior of the geometric phase based on the engineering of a three‐level atomic configuration. We analyze the effect of energy dissipation of the dynamical properties of the geometric phase and the QFI as an entanglement quantifier between the three‐level atom and field. We explore the correlation between the engineering geometric phase and QFI in the absence and presence of energy dissipation effect. We have found that the QFI is very sensitive to the effect of the time‐dependent coupling and energy dissipation.

Effects of Inclination Angles on Stepped Chute Flows

Owing to its effective energy dissipation and aeration, a stepped spillway is commonly used for flood release in hydraulic projects. Its conventional design features horizontal step surfaces. Designed for certain flow rates, it does not function satisfactorily at larger discharges. To improve this, layouts with inclined step surfaces, both downward and upward, are proposed. Computational fluid dynamics (CFD) modelling in 3D is performed to examine and compare their flow properties in the skimming flow. The results suggest that a shift from a downward to an upward layout leads to a gradual decrease in the flow velocity at the chute end; the latter exhibit higher energy dissipation efficiency. Moreover, equations are developed to estimate the velocity and energy loss. The flow velocity in the developing zone, described by a power law, shows a decline with an increase in the angle of inclination. The downward layout is subjected to somewhat higher risk of cavitation if implemented in a prototype. The extreme pressure loads acting upon an upward layout are larger, and a correlation is proposed for its prediction. On an inclined surface, either upward or downward, the pressure demonstrates an S-shaped distribution. On a vertical surface, the flow pressure increases, after an initial decline over a short distance, towards the chute bottom.

Parametric investigations of magnetic nanoparticles hyperthermia in ferrofluid using finite element analysis

Recently, magnetic nanoparticles (MNPs) based hyperthermia therapy has gained much attention due to its therapeutic potential in biomedical applications. This necessitates the development of numerical models that can reliably predict the temporal and spatial changes of temperature during the therapy. The objective of this study is to develop a comprehensive numerical model for quantitatively estimating temperature distribution in the ferrofluid system. The reliability of the numerical model was validated by comparative analysis of temperature distribution between experimental measurements and numerical analysis based on finite element method. Our analysis showed that appropriate incorporation of the heat effects of electromagnetic energy dissipation as well as thermal radiation from the ferrofluid system to the surrounding in the modeling resulted in the estimation of temperature distribution that is in close agreement with the experimental results. In summary, our developed numerical model is useful to evaluate the thermal behavior of the ferrofluid system during the process of magnetic fluid hyperthermia.

Influences of flow rate and baffle spacing on hydraulic characteristics of a novel baffle dropshaft

Due to limited flow capacity and the instability of the asymmetric structure of traditional baffle dropshafts, a novel baffle dropshaft with a symmetric structure, adopting the construction shield well directly, is proposed for large-range flow discharge in deep tunnel drainage systems. In this study, a two-phase flow field of the novel baffle dropshaft with three different baffle spacings was simulated at seven different flow rates with a three-dimensional (3D) numerical model verified with experiments, to study hydraulic characteristics of this novel baffle dropshaft. The results show that the novel baffle dropshaft has a remarkable energy dissipation effect. Baffle spacing of the novel baffle dropshaft has a greater effect on flow patterns and baffle pressure distributions than the comprehensive energy dissipation rate. Flow rate is a critical issue for the selection of baffle spacing in the design. Some guidance on baffle spacing selection and structure optimization for the application of this novel baffle dropshaft in deep tunnel drainage systems is proposed.

Dynamic performance of tire-granular material composite foundation subjected to axial and low frequency horizontal cyclic reversed loadings

Buildings in towns and villages suffer heavy damages and losses during earthquakes. In this study, six types tire–granular material composite foundations were fabricated and tested under cyclic reversed loading to investigate the energy absorption and dissipation effects of such composite foundations applied to village buildings. The effects of different axial loads (100, 200 and 300 kPa), tire arrangement and transverse connection between layers on the dynamic performance of the tire–granular material composite foundations were examined. The failure patterns of the composite foundation were obtained. The effects of the aforementioned design parameters on the dynamic performance of the composite foundation, characterised by the hysteresis loops, skeleton curves, stiffness degradation curves and energy dissipation capacity, were analysed. The hysteresis loops were full, indicating good seismic performance. The results demonstrated that using a staggered lap joint arrangement and adding a fibre mesh improved the horizontal bearing capacity and lateral stiffness of the composite foundation and enhance its overall damping capacity. Therefore, adding space connections between tires can improve the energy dissipation capacity of the foundation.

An Experimental and Theoretical Study of Wave Damping due to the Elastic Coating of the Sea Surface

Flexible plates or membranes located on the sea surface can be effective for attenuation waves approaching the beach. The most efficient structures should be found through comprehensive research using developed experiments and theory. Our experimental work was focused on the wave propagation and attenuation passing through floating elastic structures. The experiments were conducted at the wave flume of Tainan Hydraulics Laboratory, National Cheng Kung University, Taiwan. The experiment mainly analyzes the reflection coefficient, transmission coefficient and energy loss of the regular wave of intermediate water depth after passing through the elastic structure under different wave steepness and other different wave conditions. Our experiments also explore the comparison of energy dissipation effects and the differences in motion characteristics between different elastic plates and different plate fixing methods. Three elastic materials were tested in the experiments: Latex, cool cotton and polyvinyl chloride (PVC). A model of a thin elastic plate covering the sea surface was used to evaluate the effectiveness of the structure of the wave barrier. The results of experiments carried out in the wave flume were compared with theoretical predictions in a wide range of generated waves.

Investigating the Mullins Effect and Energy Dissipation in Magnetorheological Polyurethane Elastomers.

The aim of this article was to investigate the mechanical performance of magnetorheological polyurethane elastomers reinforced with different concentrations of carbonyl iron microparticles (CIPs) in which stress softening, energy dissipation, residual strains, microparticles orientation, and magnetic flux density effects will be considered. Other aspects, such as the determination of the dissipated energy during cyclic loading and unloading, were investigated by considering a pseudo-elastic network model that takes into account residual strains, magnetic field intensity, and the isotropic and anisotropic material behavior. Theoretical predictions confirmed that the material shear modulus becomes sensitive not only for higher concentrations of CIPs added into the elastomer material matrix, but also to the magnetic flux intensity that induces attractive forces between CIPs and to the strong bonds between these and the elastomer matrix. It was also found that the addition of CIPs when embedded into the polymer matrix with a predefined orientation enhances the material shear modulus as well as its capacity to dissipate energy when subjected to magnetic flux density in loading and unloading directions.

A cauliflower-shaped nickel @ porous calcium silicate core-shell composite: Preparation and enhanced electromagnetic shielding performance

Modifying magnetic metals on the surface of inorganic porous materials can not only impart conductive and magnetic ability to inorganic insulating materials, but also make full use of the rich porous structure of porous materials to absorb and consume electromagnetic energy when electromagnetic waves are incident. In this work, a cauliflower-shaped nickel-plated porous calcium silicate (Ni@PCS) functional composite with core-shell structure was successfully fabricated via electroless plating. The electromagnetic shielding performance of the prepared Ni@PCS was investigated and the corresponding electromagnetic shielding mechanism was discussed. Results indicate that the prepared Ni@PCS achieves excellent electromagnetic shielding effectiveness of 58.1 dB at X band with only 0.9 mm of sample thickness. The synergistic effect of multiple energy dissipation is the main electromagnetic shielding mechanism of this core-shell composite. The nickel shell with excellent electrical and magnetic conductivity is responsible for most of the reflection loss and magnetic loss; the interface between the PCS core and the nickel shell produces interfacial polarization loss, while the cauliflower-shaped porous structure provides the internal multiple reflection loss. The results also illustrate that coating magnetic metals on the surface of inorganic porous materials is an effective strategy to prepare high-performance electromagnetic shielding composite materials.